In harvesting operations, various binding materials are applied nowadays such as twines, nets or plastic foils with which the harvested crop formed into bales is enclosed or bound in order to simplify their handling.
Here, the tension of these binding materials should be high enough to assure a proper binding process. This tension is generated by braking or advancing arrangements in which the binding material is retarded during the binding process against the flow of the binding material stream.
DE 195 17 385 discloses a large round baler for harvested agricultural crop in which one binding arrangement is applied that includes an advancing pulley drive for the binding material such as, for example, twines, nets or foils, where the binding arrangement is provided with a braking arrangement that is switched over the advancing pulley drive in order to bring about a tension in the binding material during the binding process of the bale. The braking arrangement proposed here is connected over a linkage with the advancing pulley drive, and is applied as soon as the advancing drive is stopped, where the binding tension that was generated is maintained to the end of the binding process.
Large round balers, without advancing arrangements, have the advantage that their configurations are less costly and operate with lower levels of trouble. At high values of binding tensions, there are however, occasional problems at the start of the binding process when the retaining force on the binding material, that was generated by the rotary movement of the bale and the friction forces generated thereby on the binding material, is not sufficiently large. The result is that the binding material slips and that the binding material is not carried along after its capture.
Nevertheless, the highest possible tensions in the binding material are necessary in order to obtain good results during the binding process.
A solution for the configuration of a twine brake, that makes possible a varying tension during the binding process, is disclosed by DE 24 48 645. Here, a manual crank is used to control the position of a twine supply arm that is coupled to a pivot disk and initiates the dispensing of the binding material into the baling chamber. At the beginning of the binding process, but only after the capture of the twine by the bale, a spring mechanism is triggered as a function of the position of the pivot disk. The spring mechanism applies tension to the twine until the end position of the twine supply arm is reached after the twine has been cut by a knife. Before the beginning of the next cycle, the twine supply arm or the pivot disk is returned to the initial position and the spring mechanism is blocked. Thereby, the twine can be grasped quasi tension-free during the capture process.
Aside from these and other advantages, the binding arrangements or binding processes known from the state of the art, do however, have disadvantages.
The large round baler described in DE 195 17 385 is provided with a twine or foil guide whose tension is brought into compliance by an advance pulley drive. However, the disadvantage here is that the advance pulley drive requires higher manufacturing costs, since a larger design and technical expense must be applied, whereby in turn, the failure rate of the entire arrangement is increased.
The binding arrangement proposed in DE 24 48 645 provides for a manual control of the binding material delivery arm as a function of which a brake is actuated that increases the tension in the binding material after the twine has been grasped by the bale and maintains this tension up to the end position of the binding material delivery arm after the twine has been cut. If the tension in the twine is too high, the twine is relaxed elastically at too high a rate at the end of the binding process when the twine is cut. The result of this is that the twine recoils and wraps itself around parts or elements of the binding arrangement. Thereby, the beginning of the binding process for the following binding cycle cannot be initiated, resulting in an interruption of the process sequence.
The problem underlying the invention is seen in the need to develop, at the beginning of the binding process, only a low binding tension in order to simplify the beginning process, to increase the tension during the continuing binding process to a level as high as possible in order to attain the highest possible compression values during the binding process, and to reduce the tension again at the end of the binding process so that the problems noted initially are overcome. In particular, high cost configurations for the binding material delivery arrangement, on the one hand, should be avoided, and on the other hand, a delivery of the binding material should be accomplished independently of the operator.